My 9242 does the same thing, and I came up with the same solution as you.
However recently I would come home after work and find it had also gone into standby mode.
Now, just to verify that you and I are having the same problem, you did go into the menu <menu-8-9> and disable it, right?
I definitely disabled standby, is that the question? I've discovered that my pvr also randomly reboots for no apparent reason, but atleast when it comes back online it returns to normal TV watching instead of standby. I guess I'll have to get it replaced. Hooray for technology.